1. Field of the Invention
The present invention relates to reduction gears, and more particularly, to a reduction gear including a reduction gear mechanism having an external gear eccentrically rotatable about an input shaft; an internal gear internally being meshed with the external gear and having a small number of difference between the teeth of the internal gear and the external gear, and an output shaft for extracting a rotation of the external gear.
2. Description of the Related Art
Conventionally, there has been known a reduction gear including an input shaft, an eccentric body rotated by the rotation of the input shaft, an external gear attached to the eccentric body and swung, an internal gear internally meshing with the external gear, and an output shaft coupled to the external gear through an extracting member for extracting only an rotational component of the external gear (see Japanese Patent No. 3034630). Such a reduction gear enables the input shaft to be decelerated for rotating and rotate the output shaft.
In the above-mentioned gear reduction, however, the output shaft is arranged on an axial line of the input shaft. Therefore, the input shaft, an extracting member for extracting a rotational component of the external gear, a transmitting member for transmitting the extracted rotational component of the external gear to an output shaft, and the output shaft are arranged in the axial direction. This causes a problem that the gear reduction increases in thickness thereof and cannot be downsized. Consequently, it is difficult that an electronics device, such as a digital camera, required to be downsized employs the above reduction gear.